Compressor Clutch Circuit Diagnosis
WARNING: This page is about a different car, the 1995 Ford Aerostar. However, it is still accessible from the selected car via links, so may be relevant.
- Check System Operation
Ensure ambient temperature is greater than 50°F (10°C). Ensure battery voltage is greater than 12.5 volts. Start engine. Turn blower motor and A/C system on. If compressor clutch engages, circuit is operating properly. If compressor clutch does not engage, go to next step. - Check For Voltage
Check for voltage at A/C pressure switch. If 10 volts or greater exists, go to next step. If less than 10 volts exists, go to step 8) - By-Pass Clutch Cycling Pressure Switch
Disconnect electrical connector from clutch cycling pressure switch (located on accumulator). Ensure engine is running and A/C control panel is set to maximum cooling position. Connect jumper wire across switch harness connector terminals. If clutch engages, go to next step. If clutch does not engage, go to step 5). - Check Refrigerant Pressure
Connect manifold gauge set and note pressure readings. If pressure reading is less than 55 psi (3.9 kg/cm2 ), check system for leaks and repair as required. After repairs, verify A/C system operation. If pressure reading is greater than 55 psi (3.9 kg/cm2 ), replace clutch cycling pressure switch and verify A/C system operation. - Check Voltage At A/C Compressor Clutch Field Coil
Check for voltage at A/C compressor clutch field coil connector. If 10 volts or greater exists, go to next step. If voltage is not 10 volts or greater, go to step 7). - Check Clutch Ground
Connect jumper wire between ground terminal of A/C compressor clutch field coil and ground. If clutch engages, repair open in ground wire. If clutch does not engage, replace A/C compressor clutch field coil and go to step 1). - Check Fuse
Check fuse for continuity. If continuity exists, go to next step. If continuity does not exist, check for short or blown fuse. Repair as necessary. - Check A/C Control Switch
Ensure ignition switch is in RUN position and A/C system is in defrost position. Check for battery voltage at connector of A/C cycling switch. If battery voltage does not exist, go to next step. If battery voltage exists, go to step 10). - Check A/C Control Switch Circuit
Remove connector from A/C control switch. If 10 volts or greater exists at circuit, go to next step. If voltage is less than 10 volts, check for blown fuse or open circuit No. 294 (circuit No. 181 on Aerostar; circuit No. 326 on Explorer). Repair as necessary and go to step 1). - Check A/C Control Switch
Ensure function switch is in defrost position. Check A/C control switch and function switch for continuity. If there is continuity through function switch only, replace A/C control switch. If there is continuity through A/C control switch only, replace function switch. If there is continuity through both switches, repair open circuit between A/C control switch and clutch cycling pressure switch. Go to step 1).